1. Field of the Invention
The present invention generally relates to manufacture of multi-chip modules for semiconductor substrates and more particularly to filling gaps between chips on a module.
2. Background Description
It is desirable to wire separate chips into a single multi-chip module, while maintaining wiring density, in order to achieve a high level of integration without degrading product yield. When multiple chips are combined into a single unit, it is generally required to bind them with filler on the sides and/or front and back faces of the chips. The wiring material connecting the chips generally passes across or through this filler material. If the thermal expansion coefficient of the filler is different from that of the chips, the wires can become stressed, causing reliability fails, as a result of temperature fluctuations. Also, the filler materials are generally thermally non-conductive, and can act as a barrier to the cooling of the chips in the multi-chip module.
Currently, there is much interest in creating xe2x80x9csystem-on-a-chipxe2x80x9d solutions for different applications. The chip would include, in many cases, logic functions, and dynamic random access memory (DRAM) functions. It is difficult to integrate DRAM with logic function because they require different types of patterns and processes. Often, one must compromise on the performance of the logic and the performance/density of the memory in order to integrate them into a single chip. The use of a multi-chip module, would allow the logic and memory to be built separately, with processes optimized for each, and then combined into a single chip at the wiring levels. In an effort to combine logic and memory functions into a single chip, the chips often become very large, and the yield of the chips is very low. If the memory and logic chips are built separately, with smaller die sizes, the yields can be greatly enhanced. Then, the separate, small chips can be integrated into a single module at the wiring level.
It is therefore an object of the present invention to provide a means of matching the thermal expansion properties of the chips on a multi-chip module, and to provide a means of dissipating heat from the multi-chip module.
It is also an object of the present invention to provide a multi-chip module in which chips of different technologies can be mounted together.
The invention is a base structure on which a plurality of integrated circuit chips are mounted, the chips being electrically interconnected by conductive structures and having a given coefficient of thermal expansion. The base structure is comprised of a material that is thermally conductive, substantially electrically nonconductive, and has a coefficient of thermal expansion that approximates that of the chips.